Rotary potentiometer

ABSTRACT

A rotary potentiometer which is preferably constructed so as to be of so-called &#39;&#39;&#39;&#39;ten-turn&#39;&#39;&#39;&#39; type is disclosed. This potentiometer has a housing in which a rotor is rotatably mounted. Means are provided for rotating the rotor. A slider means located within the interior of the housing is in electrical contact with a resistance element coiled around the rotor in all positions of the rotor. A separate terminal means is used at each of the ends of the rotor for establishing electrical contact between the ends of the resistance element and the exterior of the housing.

C Unlted States Patent 11 1 1111 3,887,891 Tice June 3, 1975 [54] ROTARY POTENTIOMETER FOREIGN PATENTS OR APPLICATIONS 1 1 Inventorl Billy Harold Tice, Carlsbad, Calif 1,013,037 12/1965 United Kingdom 338/145 A :P 'Idt'lEt 'e [73] sslgnee flzgs g g5;- n erpns Primary Examiner--Thomas J. Kozma Assistant Examiner-David A. Tone Filedl S p 1973 Attorney, Agent, or Firm--Edward D. OBrian 211 App]. No.: 401,687 [57] ABSTRACT A rotary potentiometer which is preferably con- [52] US. CL. 338/l45li63138/51 Structed so as to be of so caned type is [51] Int. Cl 14c 1/43 closed This potentiometer has a housing in which a [58] Field of Search 338/145, 9, rotor is rotatably mounted Means are provided for tating the rotor. A slider means located within the in- References cued terior of the housing is in electrical contact with a re- UNITED STATES PATENTS sistance element coiled around the rotor in all posi- 2,399,060 4/1946 Puerner 338/145 X tions of the rotor. A separate terminal means is used 2,405,890 1946 Ku 145 X at each of the ends of the rotor for establishing electri- 9 1 12/1962 Hardison 8t 338/143 cal contact between the ends of the resistance element 3,346,831 10/1967 Mucher 338/145 and the exterior of the housing 3,353,133 11/1967 Bellar 338/145 I 3,562,693 2/1971 Henning..., 338/149 4 Claims, 7 Drawing Figures ISFS SHEET ROTARY POTENTIOMETER BACKGROUND OF THE INVENTION The invention set forth in this specification pertains to new and improved rotary potentiometers and more specifically to potentiometers which may be constructed so as to be of a so-called ten-turn type.

Since the fundamental principal of the potentiometer was developed in the mid-l SOOs by the German scientist Poggendorff a great deal of work has been directed towards the construction of new and improved potentiometers. Such instruments are often referred to as three terminal resistors which may be used as a potential divider. These instruments are frequently informally referred to as pots. They are used for a wide variety of electrical and electronic purposes in many different types of applications.

In spite of the fact that a great deal of work has been devoted to providing new and improved potentiometers and in spite of the fact that much of this work has been at least encouraged by an ever-increasing list of new uses for potentiometers accompanied by a frequent need for a specialized potentiometer for certain specialized types of applications it is considered that there is still a significant need for new and improved potentiometers. The exact reasons why this need is considered to exist are many, varied and complex.

Because of this it is considered that it would be impractical and effectively impossible to specifically delineate in this specification all of the reasons why new and improved potentiometers are needed. Many of the reasons for this need pertain to the costs, ease of assembly, and reliability of prior potentiometers. To be acceptable a potentiometer must be comparatively simple; must be inexpensive to construct; can be easily and conveniently installed; and, further, must be capable of rendering prolonged, effective service with a minimum of maintenance.

SUMMARY OF THE INVENTION A broad objective of the present invention is to provide new and improved rotary potentiometers to fulfill the existent need for new and improved potentiometers. Other objects of the invention are to provide new and improved potentiometers: which may be constructed at a comparatively nominal cost; which may be easily and conveniently assembled; which may be easily and conveniently installed in an operative location; and which are capable of giving prolonged, reliable, effective use with a minimum of servicing or maintenance.

In accordance with this invention these objectives are achieved by providing a potentiometer having a housing, a rotor rotatably mounted in the housing, means for rotating the rotor, a resistance element having two ends coiled around the rotor, a slider means extending between the interior of the housing and the resistance element for establishing electrical contact with the resistance element as the rotor is turned and two terminal means, each of which establishes electrical contact between an end of the resistance element and the exterior of the housing.

A potentiometer as indicated in the preceding preferably is constructed so that each of the terminal means has two parts, one of which comprises a ring located concentrically about the axis of rotation of the rotor, the other comprising brush means resiliently engaging the associated ring. One of the parts of each terminal means is mounted on the housing and the other of the parts of the same terminal means is mounted on the rotor. A potentiometer as described is also preferably formed so that the slider means includes a slider body positioned within the housing, an electrical conductor and rail means located within the housing, guide means located on the slider body for engaging the rotor as the rotor is turned so as to impart movement to the slider body causing the slider body to move along the rail means as the rotor is rotated, and spring contact means located on a slider body for resiliently engaging the resistance element and the conductor in all positions of the slider body.

A potentiometer in accordance with this invention also preferably includes a specific structure whereby each of the terminal means used establishes electrical contact with an end of the resistance element using significant spring pressure in such a manner as to facilitate assembly. In addition, a potentiometer of this invention is preferably constructed so that each of the terminal means serves as a stop for the rotor so as to prevent the slider body from being moved to such an extent that it is displaced from an operative position. By serving in this regard each of the terminal means in effect serves a dual function. This, of course, influences the simplicity and desirability of the potentiometer as herein described.

BRIEF DESCRIPTION OF THE DRAWINGS Further details of a potentiometer in accordance with this invention are best more fully indicated by referring to the accompanying drawings in which:

FIG. 1 is an isometric view of a presently preferred embodiment or form of a potentiometer in accordance with this invention;

FIG. 2 is a cross-sectional view taken at line 2--2 of FIG. 1;

FIG. 3 is a cross-sectional view taken at line 3--3 of FIG. 2;

FIG. 4 is a cross-sectional view taken at line 4--4 of FIG. 2;

FIG. 5 is a partial cross-sectional view taken at line 5--5 of FIG. 2;

FIG. 6 is a cross-sectional view corresponding to a cross-sectional view taken at line 6-6 of FIG. 2 showing the positions of various parts at one extreme adjustment position of the potentiometer; and

FIG. 7 is a cross-sectional view corresponding to FIG. 4 illustrating the positions of various parts at the other extreme adjustment position of this potentiometer.

The precise potentiometer illustrated in the drawings is but a single unit embodying certain essentially intangible concepts or features as are set forth invthe appended claims. Those skilled in the construction of potentiometers will realize that these concepts and features can be utilized in various potentiometers which differ from the precise potentiometer illustrated as to matters of routine design or engineering skill in the field of this type of electrical instrument.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawings there is shown a potentiometer 10 in accordance with this invention which includes a generally cylindrical, electrically non-conductive housing 12 having a generally flat front end 14 and a generally flat rear end 16. Within the interior of this housing 12 extending between the ends of it are two rails 18 and 20 which extend parallel to the axis of the housing 12. Within the interior of the housing 12 there is also a small internal flange 22 which extends parallel to the rails 18 and 20. The rail 18 and the flange 22 are provided with recesses 24 which face one another. These recesses 24 are designed so as to hold an elongated, flat electrical conductor 26 so that it extends between the ends 14 and 16 parallel to the axis of the housing 12. This conductor 26 includes a terminal tab 28 extending out through a small opening 30 in the housing 12 adjacent to the rear end 16.

The rear end 16 of the housing 12 carries an internally projecting cylindrical boss 32 having a centrally located cylindrical bearing cavity 32 formed therein. This boss 32 and this cavity 34 are axially aligned with a bearing opening 36 in the front end 14 and with the axis of the housing 12. An elongated shaft 38 is positioned so as to extend through the bearing opening 36 so that an axially aligned cylindrical boss 40 on an end of the shaft 38 extends into and is supported within the cavity 34. The end of the shaft 38 extending from the housing 12 carries a conventional slot 42 designed to be engaged by a screwdriver or a suitable instrument handle or the like (not shown) used in adjusting this potentiometer.

The shaft 38 also carries exteriorly of the housing 12 a bushing 44 having a threaded section 46 capable of being used in mounting this potentiometer 10 in a conventional manner. The bushing 44 also includes a terminal flange 48 which fits into and is secured to the interior of a disclike cavity 50 in the front end 14. This bushing 44 is held in place against slipping off of the shaft 38 through the use of a conventional U-shaped snap ring 52 fitting within a groove 54 in the shaft 38.

Within the interior of the housing 12 the shaft 38 is secured to an interior bore 56 within a non-conductive rotor 58 by means of knurling 60 on the shaft 38 engaging the interior of this bore 56. The bore 56 is centrally located along the axis of this rotor 58 and this rotor 58 is of a generally cylindrical configuration. Around the exterior of the rotor 58 a continuous groove 62 is located so as to extend in what may be referred to as a coiled or helical path. A conventional resistance element 64 is disposed in this groove 62 so as to be coiled around the rotor 58 between the ends 66 and 68 of the rotor. These ends 66 and 68 are provided with dished out annular recesses 70 which are spaced both from the shaft 38 and the periphery of the rotor 58. Internal cavities 72 are located in the ends 66 and 68 of the rotor 58 so as to extend from the bottoms of the recesses 70 beneath the resistance element 64 adjacent to the ends 74 and 76 of this element.

Annular metallic slip ring plates 78 are located within these recesses 70. These plates 78 carry resilient generally U-shaped tabs 80 which fit within the cavities 72 and resiliently bear against the bottoms of the ends 74 and 76 of the resistance element 64 so as to establish electrical conduction with the resistance element 64.

These slip ring plates 78 are resiliently engaged at all times by the bent extremities 82 of yokes 84 of terminal 7 plates 86. These terminal plates 86 rest against the front and rar ends 14 and 16 of the housing 12 to one side of the shaft 38. Each of them is provided with a tab ,1

88 extending out through an opening 90 in the housing For convenience of mounting small projections 92 on the front and rear ends 14 and 16 may extend to openings 94 in the terminal plates 86 and may be headed over in accordance with conventional practice. With this construction the yokes 84 in effect straddle the shaft 38 so that the extremities 82 serve as brushes resiliently engaging the plates 78 at diametrically opposite sides of the shaft 38. It will be apparent from the above that the terminal plates 86 and the plates 78 together with their associated parts serve as terminal means in the potentiometer 10 adjacent to the ends 74 and 76 of the resistance element 64.

In addition to serving this function the plates 78 carry small extensions 96 which extend outwardly of the periphery of the rotor 58 through notches 98 for the purpose of serving as stops for a slider body 100. This slider body 100 is formed of a non-conductive material so as to include enlarged ends 102 located between the periphery of the rotor 58 and the interior of the housing 12 against the surfaces of the rails 18 and 20 which are remote from one another. The slider body 100 also includes arc-like interior guides 104 which are located parallel to one another between the ends 102 in an orientation corresponding to the sloping of the resistance element 64 around the rotor 58. These guides 104 fit on opposite sides of the resistance element 64 so as to be guided along this resistance element 64 as the shaft 38 is turned in such a manner as to cause the slider body 100 to move linearly between the ends 14 and 16 of the housing 12.

During such movement a resilient, electrically conductive spring contact element 106 having a somewhat U-shaped configuration is held by spring pressure so that its ends 108 are in constant spring pressure against the conductor 26 and the resistance element 64. This contact element 106 extends around a pin 110 projecting between the guides 104 on the slider body 100 so as to be held in place by this pin 110 and by engagement with the facing surfaces (not separately numbered) of the guides 104. If desired a central enlargement 112 may be located on the slider body 100 adjacent to the pin 110. When the enlargement 112 is used it should preferably fit within the interior of the housing 12 as shown so as to tend to reinforce the slider body 100.

It is believed that the operation of the potentiometer 10 will be obvious from the aforegoing description of the parts of this instrument. As it is used the shaft 38 will be turned in the conventional manner so as to cause the slider body 100 to be moved along the length of the housing 12 between the ends 14 and 16. During such movement of the slider body 100 it will move in a linear path. Movement of the slider body 100 so that the contact element 106 past where the resistance element 64 is terminated by the tabs 80 on the plates 78 is prevented by the extensions 96 on the plates 78 hitting against either of the ends 102'on the slider body 100. This is considered to be an important advantage with the construction of the potentiometer 10.

The potentiometer 10 is, however, considered to be desirable from a number of other standpoints. Because of the way the various parts are constructed and assembled this potentiometer 10 is considered to be relatively easy to assemble; it is considered that this potentiometer 10 can be manufactured at comparatively nominal cost. Because of the construction of the potentiometer 10 it is considered capable of providing prolonged, ef-

fective, reliable service with a minimum of maintenance.

I claim:

1. A potentiometer having a cylindrical housing, a rotor rotatably mounted in said housing, means for rotating said rotor, a resistance element coiled around said rotor, slider means extending between the interior of said housing and said resistance element for establishing electrical contact with said resistance element as said rotor is turned and two terminal means, each of said terminal means establishing electrical contact between an end of said resistance element and the exterior of said housing in which the improvement comprises:

each of said terminal means having two parts, the

first of said parts comprising a ring located concentrically about the axis of rotation of said rotor, the first of said parts of both of said terminal means being located on said rotor, the second of said parts comprising brush means resiliently engaging the associated ring, the second of said parts of both of said terminal means being located within the interior of said housing and including yokes straddling said shaft, the ends of said yokes comprising said brush means, said rings on both of said terminal means being mounted on the ends of said rotor and include resilient tabs extending underneath said resistanceelement, said tabs being located adjacent to the ends of said resistance element and resiliently engaging said resistance element so as to serve as end terminals therefor,

said slider means including a slider body positioned 3 within said housing between the exterior of said rotor and the interior of said housing, an electrical conductor mounted on the interior of said housing so as to extend parallel to the axis of said rotor, rail means engaging said slider body and extending parallel to the axis of rotation of said rotor located on the interior of said housing, said rail means being said slider body for resiliently engaging said resis-' tance element and said contact strip in all positions of said slider body,

said rings on both of said terminal means including extensions extending therefrom beyond the periphery of said rotor, said extensions serving as stops to limit movement of said slider body and said rotor as said shaft is rotated,

tab means for making an electric connection integrally formed with the second of said parts of both of said terminal means, said tab means extending from the interior of said housing to the exterior of the periphery of said housing.

2. A potentiomer as claimed in claim 1 wherein:

said rail means comprise two separate rails which are spaced from and parallel to 'one another,

said slider body has two enlarged ends which are spaced from one another so as to engage the surfaces of the said rails which are spaced from one another so as to prevent rotation of said slider body as said rotor is turned.

3. A potentiometer as-claimed in claim 2 wherein:

said conductor is mounted on said housing between said rails, and

said contact means comprises a spring resiliently engaging said resistance element and said conductor, said spring being mounted on said slider body.

4. A potentiometer as claimed in claim 1 wherein:

said rail means comprise two separate rails which are spaced from and parallel to one another,

said slider body has two enlarged ends which are spaced from one another so as to engage the surfaces of the said rails which are spaced from one another so as to prevent rotation of said slider body as said rotor is turned,

said resistance element extends from said rotor, and

said guide means are parallel guides engaging opposite sides of said resistance element,

said conductor is mounted on said housing between said rails, and

said contact means comprises a spring resiliently engaging said resistance element and said conductor,

said spring being mounted on said slider body. =l 

1. A potentiometer having a cylindrical housing, a rotor rotatably mounted in said housing, means for rotating said rotor, a resistance element coiled around said rotor, slider means extending between the interior of said housing and said resistance element for establishing electrical contact with said resistance element as said rotor is turned and two terminal means, each of said terminal means establishing electrical contact between an end of said resistance element and the exterior of said housing in which the improvement comprises: each of said terminal means having two parts, the first of said parts comprising a ring located concentrically about the axis of rotation of said rotor, the first of said parts of both of said terminal means being located on said rotor, the second of said parts comprising brush means resiliently engaging the associated ring, the second of said parts of both of said terminal means being located within the interior of said housing and including yokes straddling said shaft, the ends of said yokes comprising said brush means, said rings on both of said terminal means being mounted on the ends of said rotor and include resilient tabs extending underneath said resistance element, said tabs being located adjacent to the ends of said resistance element and resiliently engaging said resistance element so as to serve as end terminals therefor, said slider means including a slider body positioned within said housing between the exterior of said rotor and the interior of said housing, an electrical conductor mounted on the interior of said housing so as to extend parallel to the axis of said rotor, rail means engaging said slider body and extending parallel to the axis of rotation of said rotor located on the interior of said housing, said rail means being engaged by said slider body so that rotation of said slider body is prevented, guide means located on said slider body for engaging said rotor for moving said slider body along said rail means as said rotor is rotated, and spring contact means located on said slider body for resiliently engaging said resistance element and said contact strip in all positions of said slider body, said rings on both of said terminal means including extensions extending therefrom beyond the periphery of said rotor, said extensions serving as stops to limit movement of said slider body and said rotor as said shaft is rotated, tab means for making an electric connection integrally formed with the second of said parts of both of said terminal means, said tab means extending from the interior of said housing to the exterior of the periphery of said housing.
 1. A potentiometer having a cylindrical housing, a rotor rotatably mounted in said housing, means for rotating said rotor, a resistance element coiled around said rotor, slider means extending between the interior of said housing and said resistance element for establishing electrical contact with said resistance element as said rotor is turned and two terminal means, each of said terminal means establishing electrical contact between an end of said resistance element and the exterior of said housing in which the improvement comprises: each of said terminal means having two parts, the first of said parts comprising a ring located concentrically about the axis of rotation of said rotor, the first of said parts of both of said terminal means being located on said rotor, the second of said parts comprising brush means resiliently engaging the associated ring, the second of said parts of both of said terminal means being located within the interior of said housing and including yokes straddling said shaft, the ends of said yokes comprising said brush means, said rings on both of said terminal means being mounted on the ends of said rotor and include resilient tabs extending underneath said resistance element, said tabs being located adjacent to the ends of said resistance element and resiliently engaging said resistance element so as to serve as end terminals therefor, said slider means including a slider body positioned within said housing between the exterior of said rotor and the interior of said housing, an electrical conductor mounted on the interior of said housing so as to extend parallel to the axis of said rotor, rail means engaging said slider body and extending parallel to the axis of rotation of said rotor located on the interior of said housing, said rail means being engaged by said slider body so that rotation of said slider body is prevented, guide means located on said slider body for engaging said rotor for moving said slider body along said rail means as said rotor is rotated, and spring contact means located on said slider body for resiliently engaging said resistance element and said contact strip in all positions of said slider body, said rings on both of said terminal means including extensions extending therefrom beyond the periphery of said rotor, said extensions serving as stops to limit movement of said slider body and said rotor as said shaft is rotated, tab means for making an electric connection integrally formed with the second of said parts of both of said terminal means, said tab means extending from the interior of said housing to the exterior of the periphery of said housing.
 2. A potentiomer as claimed in claim 1 wherein: said rail means comprise two separate rails which are spaced from and parallel to one another, said slider body has two enlarged ends which are spaced from one another so as to engage the surfaces of the said rails which are spaced from one another so as to prevent rotation of said slider body as said rotor is turned.
 3. A potentiometer as claimed in claim 2 wherein: said conductor is mounted on said housing between said rails, and said contact means comprises a spring resiliently engaging said resistance element and said conductor, said spring being mounted on said slider body. 